1. Field of the Invention
The present invention relates to machine tools and detachable/attachable motors.
2. Description of the Related Art
(1) Some machine tools that use a machining center etc. to machine workpieces in a processing area have, in the processing area, a rotating table apparatus that rotatably holds a workpiece (see JP 2003-311565A (pages 4 and 5)). Such machine tools process workpieces as follows.
First, an unprocessed workpiece is carried into the processing area and this workpiece is held by the rotating table apparatus. The workpiece is then continuously or intermittently rotated in a suitable way as it is processed by a tool of the machining center. After processing, the processed workpiece is removed from the rotating table apparatus and carried out of the processing area.
When there is trouble with the rotating table apparatus, however, processing cannot be performed until the rotating table apparatus is repaired, and this may lower the operating rate of the machine tool.
A structure that is provided with a plurality of rotating table apparatuses 321 that can be carried into and out from a processing area A1 as shown in FIG. 19 is a conceivable reference example of a machine tool that is capable of solving the above-mentioned problem. If each rotating table apparatus 321 holds a workpiece W and is on standby in a work area other than the processing area A1, then, in the event that there is trouble with the rotating table apparatus 321 undergoing processing in the processing area A1, one of rotating table apparatuses 321 on standby can be carried into the processing area A1 so that processing can be resumed quickly, thus keeping the operating rate of the machine tool 301 from dropping.
However, the drive source of the rotating table apparatuses 321 generally is a motor 361 to which power is supplied through an associated power cable 362. For this reason, there is a possibility that, in the course of moving the plurality of rotating table apparatuses 321 into and out of the processing area A1, their power cables 362 may become tangled.
(2) Incidentally, an electric motor 2461 (hereinafter, referred to as “motor”) is used as a drive device that is connected to a driven rotation shaft and applies a rotational force thereto. The motor 2461 is a device that converts electrical power into motive power.
FIG. 32 is a central cross-sectional view for describing an example of the structure of the motor 2461.
As shown in the figure, the motor 2461 is provided with a cylindrical stator 2464 and a rotor 2463 that is accommodated in the space within the stator 2464 and that is rotatably supported at its two ends by a pair of bearings 2468 provided in the stator 2464. A permanent magnet 2467 is provided on the outer circumferential surface of the rotor 2463, whereas a plurality of coils 2466 are arranged on the inner circumferential surface of the stator 2464 at an interval of a predetermined angle in the circumferential direction. By sending an alternating current through the coils 2466 while maintaining the phase difference that corresponds to this predetermined angle, the permanent magnet 2467 is magnetically drawn toward the coils 2466 in the circumferential direction in sequence, causing rotation of the rotor 2463 (for example, see JP 8-163844A (pages 2 to 4 and FIG. 1).
In a case where the driven rotation shaft 2441, which is axially supported by a predetermined support member 2427, is rotated using a motor such as the motor 2461, the rotor 2463 of the motor 2461 is connected to the driven rotation shaft 2441 through an intermediate element 2451 such as a coupling. Once connected, the motor is used under the assumption that it will not be disconnected except for repair or maintenance.
In some cases, however, it may be preferable to adopt a structure in which the motor 2461 can be attached and detached (that is, “connected” and “disconnected” as referred to above) to and from the driven rotation shaft 2441. One such case is where a single motor 2461 is used in common for a plurality of driven rotation shafts 2441. If such attachment/detachment is possible, then it is conceivable that the structure of the motor 2461 can be made simpler and more compact compared to that described above. Currently, however, no such motors 2461 are available on the market.